Set Agent Contact Identifier

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true and idempotentHint=true, but the description adds meaningful context: only the description marker changes, the change is verified by readback, and the label is untrusted display text rather than routing identity. This goes beyond what the annotations convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, front-loaded with the action and scope, followed by the prerequisite and trust caveat. Every sentence carries information, though the semicolon structure is slightly dense.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter setter with no output schema, the description covers what is changed, the prerequisite, and the trust semantics of the label. It is nearly complete, though it could say more about overwrite behavior or error cases.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents both parameters fully. The description reinforces ownership and the trusted-display nature of the identifier but adds no syntax or format detail beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb and resource: "Label your own Event channel or legacy outbox", making it clear this sets a display label on an owned catalog entry. It does not explicitly differentiate itself from siblings like set_contact_status or update_data_type, but the object and effect are unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives a prerequisite ("Requires an unambiguous owned catalog entry") and scope ("your own Event channel or legacy outbox"), which implies when to use it. However, it offers no explicit when-not conditions or named alternatives, leaving the agent to infer boundaries.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.